Choke Adjustment Needle

Robert/Texas

Robert/Texas

Well-known member
The mounting flange on my ’28 roadster’s carburetor broke so I replaced it with a known good one. Now I’m going nuts trying to get the choke adjustment needle working. The red book has not been much help for this. Any advice would be much appreciated.

Thank you, Robert.
 
When you say flange, are you talking about the intake side or the top of the carb? Can you take a photo?
 
More details would be helpful. Are you talking about the GAV (Gas Adjustment Valve) that turns in the brass tube in the carburetor and are you having problems getting it to turn properly? Or are you talking about the connection to the rod that runs up into the inside of the car?
 
Robert/Texas said:
The mounting flange on my ’28 roadster’s carburetor broke so I replaced it with a known good one. Now I’m going nuts trying to get the choke adjustment needle working. The red book has not been much help for this. Any advice would be much appreciated.

Thank you, Robert.
Click to expand...

Need more info. Are we discussing a Zenith? And if so are we discussing the GAV?

If I remember correctly, the early Zeniths had a brass "seat" that the GAV needle went into. Later models, the seat was machined into the carb casting. There was a thread on reburbishing that seat with a Dremmel sometime back.
 
zenithpic.jpg

Notice the adjusting needle and it's A9528 housing - which screws into the carburetor body. The housing has "fingers" which hold the adjusting needle in whatever position you place it.

What can happen is modern reproductions are frequently not made well, and not to "size." The needle can turn VERY TIGHTLY in the housing.

The solution may be to run a drill slightly smaller than the diameter of the needle down through the A9528 housing WHILE THE CIRCLE CLIP IS IN PLACE.

You could try removing the circle clip first and try the needle with the "finger pressure" alone.

I have tried "bending" the fingers out to make the pressure on the needle less. I drove an ice-pick down the hole. But proceeded to break off one of the fingers - alas. BUT with one finger removed, with the clip added, the needle turns fine - so that one wasn't a total loss.

As to the seat, the only point where that comes into play is when you have the GAV totally shut off - a condition you almost never run in real life. It's purpose really is just a starting point to get to that "quarter turn" or whatever your engine runs best at.

Another issue I have seen is the threads in the housing are not "co-linear" with the A9528 housing body. This results in the "half moon" of the adjusting needle to strike and bind on the interior of the A9528 bushing/housing. No good solution to that other than getting another housing.

Joe K
 
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Thanks for trying to help me.
Yes, it is the GAV, the choke works but the adjustment is jammed, I can’t turn the knob. The carburetor bowl is marked Zenith and is not the early type. One of the bolt holes that mounts the carb to the intake manifold cracked and the engine stalled. The engine had been running well for years before this happened. I replaced that top of the carb with another one that I had on hand.
Yesterday afternoon I drove 95 miles to my cabin in a rural area where I keep my old Fords stored in my barn. The car started right up so I drove it to my workshop. As soon as it warms up, I’ll start working on it again. I’m 90 years and my fingers and thumbs don’t work like they used to.
 
Loosen the 2 bolts that hold the carburetor to the intake manifold, then see if the GAV rod will turn.
 
Katy has a good suggestion. Sometime the connection to the rod is not formed right and binds things up. I have fixed that with new parts.

Joe K also has some good comments. I have remove the ring as he suggested to fix the problem there.
 
Try backing out the GAV (adjusting needle housing) about 1 to 2 turns. Then try turning the adjusting needle. Turn the adjusting needle out a couple of turns, then retighten the needle housing. You probably tightened the housing with out first backing out the needle.
 
BINGO, loosening the two bolts worked but I also found that the GAV rod will not go through the bracket on the gas tank and firewall without bending it. A previous owner had bent it, but a repro one goes through if I force it. The rubber grommet is missing in the firewall but there is one in the bracket. I'm having company tomorrow and I have some medical appointments next week so it will take some time to work on those issues.
Thanks again for all your help.
 
If the carburetor was lower would the rod angle be OK? If this is the case, you could add a spacer at the flange.

Enlarging the hole in the firewall may help. A fender washer at the top of the rod where it goes through the hole will close up the hole.
 
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